The present disclosure relates to printed circuit boards, and more specifically, to backdrilling in vias of printed circuit boards.
Often multiple vias may be used in a multi-layered printed circuit board to electrically connect conductive traces in differing conductive layers of the board. During the manufacturing of the printed circuit board, the vias may be created by plating predrilled holes in the board with a conductive material (typically Copper). The entire depth of the via, including an unused portion of the via called a stub, may be plated with the copper material. In this context, a stub may refer to the portion of the via extending beyond an intended trace escape layer within the board. Left unchanged, the plated stub portion may adversely degrade electrical signals traveling through the desired portion of the via (i.e., into the desired trace escape layer) during use of the completed circuit board.
In order to reduce the impact of stubs on circuit board performance, the stubs may be removed from the board, or at least shortened, during the manufacturing process. One method for removing stubs is called backdrilling. In this process, a drill bit, preferably one which has a slightly larger diameter than the bit used in predrilling the hole for the via (prior to plating), may be used by a drill for boring into the via and removing the plating material from its stub portion. Once the undesirable plating material is carved out, and the stub is effectively removed, the stub's negative impact on electric signals passing through the board may be substantially reduced.